Muffler and muffler core puncher

ABSTRACT

The muffler has an outer shell filled with fiberglass wool around a central core tube which conveys the exhaust gases. The core tube is punched from the inside to form a spiral pattern of holes having gas deflecting tongues which project outward in circumferential directions opposed to the direction of the spiral. When the muffler is to be used on an engine producing a stream of exhaust gas having clockwise rotation in the core tube, the spiral pattern of holes is clockwise and the gas is discharged from the holes in counterclockwise directions. For a counterclockwise rotating gas stream the spiral pattern of holes is formed in counterclockwise direction and the tongues deflect the gas from the holes in clockwise directions. The holes are punched and the deflecting tongues are formed by a radial punch which reciprocates through a guide hole in a support tube. The punch is mounted on a crankshaft which rocks the punch back and forth as it is projected and retracted. When a core tube is placed on the support tube the rocking motion of the punch rotates the core tube to properly space the holes circumferentially. By slowly moving the core tube axially, the desired spiral pattern of holes is produced. The direction of the spiral, as a right-hand or left-hand thread, is determined by the direction of rotation of the crankshaft.

United States Patent 1191 McFadden 11] 3,811,352 451 May 21, 1974 MUFFLER AND MUFFLER CORE PUNCHER [76] Inventor: Lawrence D. McFadden, 3915 NE.

Stanton, Portland, Oreg. 97212 [22] Filed: Apr. 26, 1973 [21] Appl. No; 354,678

Primary Examiner-Willie G. Abercrombie Attorney, Agent, or Firm-Lee R. Schermerhorn ABSTRACT The muffler .has an outer shell filled with fiberglass wool around a central core tube which conveys the exhaust gases. The core tube is punched from the inside to form a spiral pattern of holes having gas deflecting tongues which project outward in circumferential directions opposed to the direction of the spiral. When the muffler is to be used on an engine producing a stream of exhaust gas having clockwise rotation in the core tube, the spiral pattern of holes is clockwise and the gas is discharged from the holes in counterclockwise directions. For a counterclockwise rotating gas stream the spiral pattern of holes is formed in counterclockwise direction and the tongues deflect the gas from the holes in clockwise directions.

The holes are punched and the deflecting tongues are formed by a radial punch which reciprocates through a guide hole in a support tube. The punch is mounted on a crankshaft which rocks the punch back and forth as it is projected andretracted. When a core tube is placed on the-support tube the rocking motion of the punch rotates the core tube to properly space the holes circumferentially. By slowly moving the core tube axially, the desired spiral pattern of holes is produced. The direction of the spiral, as a right-hand or left-hand thread, is determined by the direction of rotation of the crankshaft.

7 Claims, 6 Drawing Figures MUFFLER AND MUFFLER CORE PUNCI-IER BACKGROUND OF THE INVENTION This invention relates to improvements in an internal combustion engine muffler and a muffler core tube puncher.

As long as internal combustion engines have been in use, attempts have been made to improve the exhaust mufflers for such engines in order to reduce the noise of the exhaust to an acceptable level without imposing an unacceptable back pressure on the engine.,These two requirements being mutually inconsistent, most attempts to improve mufflers have complicated the structure to the point of impracticality from the cost standpoint. Since a muffler is in the nature of an accessory device which does not improve the performance of the engine, a high manufacturing cost is not acceptable.

Objects of the invention are, therefore, to provide an improved exhaust muffler for internal combustion engines, to provide a muffler which reduces the exhaust noise to an acceptable level without causing an unacceptable back pressure in the engine, to provide a muffler of the type described which may be manufactured at relatively low cost, to provide a muffler which transforms the unpleasant exhaust noise into a more pleasant sound, to provide a novel method for punching a core tube for a muffler, and to provide a simple and practical apparatus for carrying out the method.

SUMMARY OF THE INVENTION The most effective way to minimize back pressure on the engine is to provide a straight through core tube free of baffles which deflect the main stream of exhaust gas in different directions, making a tortuous passage through the muffler. However, a straight through core tube ordinarily requires a very long muffler and, consequently, high cost in order to attenuate the sound to an acceptable level. In such a muffler the core tube is perforated to discharge the high pressure impulses into a porous material in an outer casing surrounding the core length of the muffler for a corresponding reduction in.

the sound. In other words, a short muffler embodying the invention will be just as effective as a much longer conventional type of muffler.

Further. the sound deadening effect is enhanced by not cutting unrestricted openings in the core tube. According to the invention, the core tube is punched from the inside in such a manner as to leave metal deflecting tongues projecting angularly in circumferential directions from the outside of the core tube. Preferably, the direction assumed by these tongues is counter to the direction of the circular flow of the exhaust gas so that the exhaust gas escapes from the core tube openings in a backward circumferential direction.

This can be accomplished because it is found that the exhaust stream from most engines rotates in a clockwise direction as viewed from the input end of the muffler. For use on engines having a counterclockwise exhaust flow, the direction of the spiral pattern of core tube openings and the directions of the' deflecting tongues may be reversed.

The holes are punched and the deflecting tongues are formed by a radial punch which reciprocates through a guide hole in a support tube. The punch is mounted on a crankshaft which rocks the punch back and forth as it is projected and withdrawn. When a core tube is placed on the support tube, the rocking motion of the punch rotates the core tube to properly space the holes circumferentially. By slowly moving the core tube axially, a spiral pattern of holes is produced.

The invention will be better understood and the foregoing and other objects and advantages will become apparent from the following detailed description of the preferred embodiment of muffler and apparatus illustrated on the accompanying drawing. Various changes may be made, however, in the details of construction and arrangement of parts and certain features may be used without others. All such modifications within the scope of the appended claims are included in the inventlOl'l BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of a core tube bodying the invention;

FIG. 2'is an enlarged longitudinal sectional view of the distal end portion of the support tube in FIG. 1;

FIG. 3 is an enlarged view on the line 3-3in FIG.

puncher em- DESCRIPTION OF THE PREFERRED EMBODIMENT 'The proximal end of a cantilever support tube 10 is rigidly mounted in a pair of clamps 11 and 12 on a bench 13. In the distal end of support tube 10 screws 14 secure a bronze bushing 15 supporting the distal end of a crankshaft 16. A similar bushing, not shown, supports the proximal end of crankshaft 16 in the region of clamp 12. These bushings are lubricated by a tank oiler 17 which admits oil into support tube 10 under the control of a metering valve 18. Crankshaft 16 is rotated continuously in the direction of the arrow in FIG. 3 by means of motor 20 and angle drive unit 21.

Screws 14 also secure one end of a stationary sleeve 25 in the distal endof support tube 10. Sleeve 25 contains a crankshaft extension 26 which has an eccentrically located hole 27 in its proximal end to receive a crankpin 30 on the distal end of crankshaft l6. Crankpin 30 is secured in hole 27 by a taper pin 31.

The distal end of crankshaft extension 26 is supported by a bronze bearing 32 secured in the distal end of sleeve 25 by screws 33. This bearing is lubricated by annular grooves 34. Sleeve 25 forms an oil reservoir for supplying the grooves 34 through a longitudinal groove (not shown), the sleeve having an opening at 36 in FIG. 3 for adding oil to the reservoir. This reservoir also supplies oil to the distal end of bronze bushing 15. A steel thrust plate 37 is secured to the distal end of crankshaft extension 26 by a screw 38.

A punch carrier 40 is rotatably mounted on crankpin 30 between the end of crankshaft l6 and the end of crankshaft extension 26, the punch carrier being equipped with an oil hole 41 in communication with the oil reservoir in sleeve 25. A punch 45 has a threaded shank 44 mounted in a radial threaded hole in punch carrier 40. The rotation of crankpin 30 reciprocates and rocks punch 45 back and forth in a punch guide hole 46 in sleeve 25.

FIG. 3shows punch 45 fully retracted so that it does not protrude from guide hole 46. As crankpin 30 rotates counterclockwise about the axis of shaft 16,

punch 45 is projected through guide hole 46, rocked clockwise through asmall angle and retracted back into hole 46. Thus, when a muffler core tube T having an inside diameter only slightly larger than the outside diameter of sleeve 25 is placed over the sleeve 25, the outward movement of the punch punches a hole 50 in the core tube and the clockwise. rocking of the punch as it is being projected and retracted bends outward a tongue of metal 51 on the upper side of the punch, leaving the tongue protruding at an angle in a counterclockwise direction as the punch begins to retract. The clockwise rocking movement of the punch as it is being extended and retracted also rotates the core tube T in a clockwise direction. i a

As shown in FIG. 4, the counterclockwise rotation of crankshaft 16 is indicated by arrow 55, punch 45 protrudes radially and rocks clockwise as indicated by arrow 56 and this movement drives tube T clockwise as indicated by arrow 57. The tube T is rotated far enough by the rocking action of punch 45 asit protrudes and retracts so that the next projection of the punch does not cause it to re-enter the hole 50 but instead the punch forms a new hole adjacent the lower side of the termined by an adjustable stop collar 60 clamped on tube 10.

As previously explained, it is desirable to spiral the openings 50 in the same direction as the rotation of the gas stream which will flow through the tube T in the muffler. ln most automobile engines the exhaust stream is found to rotate in the direction of a right-hand thread so, in the present illustration, the openings 50 are shown as spiralling in the direction of a right-hand thread. For engines where the exhaust stream spirals in the opposite direction in the exhaust pipe, the spiral pattern of opening 50 in exhaust tube T may be reversed by reversing the direction of rotation of crankshaft 16 from counterclockwise to clockwise. in either case the tongues 51 project in the opposite circumferential direction to reverse the direction of the gas streams emerging from openings 50.

After the holes 50 have been formed, the ends of tube T are welded'in the ends of a conventional mufi'ler shell S, the space between the tube and shell being filled with a porous packing 61, such as glass wool or the like. End fittings 62 and 63 are also welded on.

Referring now to H6. 6, the arrow 65 indicates the direction of rotation of a stream of exhaust gas flowing through tube T with spiral flow in the direction of a right-hand thread. The small streams of gas momentarily escaping through holes 50 are deflected by tongues 51 into counterclockwise directions as indicated by arrows 66. Since the gas cannot escape from shell S except by flowing back into tube T, all the small streams 66 must pass again through holes 50 and re-enter tube T. ln order to do'this, the streams 66 must reverse direction again after each pressure wave or pulse has passed in order to get around the tongues 51. These circuitous flow paths of the streams 66 absorb energy and produce the desired muffling effect on the sound of the exhaust without introducing undesirable back pressure on'the motor because there are no baffles or other obstructions in the tube T. The improved 'efiectiveness of energy absorption allows a shorter length of muffler.

To punch a core tube T for use on an engine having an exhaust stream spiralling in the direction of a lefthand screw in the exhaust pipe, it is only necessary to reverse the direction of rotation of crankshaft 16. Then the tongues 15 are angled in the opposite direction and the spiral path of openings 50 and tongues 15 assumes the direction of a left-hand thread around tube T. In comparison with FIG. 6, the direction of rotation of the gas flow at 65 would be counterclockwise instead of clockwise and the directions of tongues 51 and individ ual streams 66 would be clockwise instead of counterclockwise whereby the desired reversals of flow and effective muffling action would be accomplished in the manner described above.

Although a spiral pattern of openings 50 is preferred, the openings may be arranged in separate circular patternsjf desired by shifting tube T axially on support tube 10 after a complete ring of openings has been formed instead of after each punching operation.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by letters Patent is:

l. A muffler core tube puncher comprising means to support the core tube internally, a punch in said support means, and means to actuate said punch outwardly in radial and circumferential movements so as to punch a hole in said tube and bend out a tongue of the tube material on one side of said hole.

2. A core tube punch as defined in claim 1, said actuating means comprising a crankshaft having a crankpin, and a punch guide hole in said support means, said punch being mounted on said crankpin and being guided by said guide hole in said radial and circumferential movements. I

3. A core tube punch as defined in claim 2, said support means comprising a sleeve containing said crankshaft. v

4. A core tube punch as defined in claim 2, said support means comprising a cantilever-mounted stationary tube containing said crankshaft, a stationary sleeve mounted on the free end of said tube as an extension of said tube, said punch guide hole being in said sleeve, a crankshaft extension in said sleeve connected with said crankpin, and a bearing in said sleeve for said crankshaft extension.

5. The method of punching a muffler core tube comprising supporting said core tube internally for rotation on its axis, and projecting a punch outwardly and circumferentially through said core tube to punch a hole 5 6 in said tube and bend out a tongue on one side of said 7. The method of claim 6 including retracting said hole. punch and moving said tube axially after each punching- 6. The method of claim 5 including causing said ciroperation to punch a spiral pattern of holes in said cumferential movement of said punch to rotate said tube. tube into position for punching another hole. 5 

1. A muffler core tube puncher comprising means to support the core tube internally, a punch in said support means, and means to actuate said punch outwardly in radial and circumferential movements so as to punch a hole in said tube and bend out a tongue of the tube material on one side of said hole.
 2. A core tube punch as defined in claim 1, said actuating means comprising a crankshaft having a crankpin, and a punch guide hole in said support means, said punch being mounted on said crankpin and being guided by said guide hole in said radial and circumferential movements.
 3. A core tube punch as defined in claim 2, said support means comprising a sleeve containing said crankshaft.
 4. A core tube punch as defined in claim 2, said support means comprising a cantilever-mounted stationary tube containing said crankshaft, a stationary sleeve mounted on the free end of said tube as an extension of said tube, said punch guide hole being in said sleeve, a crankshaft extension in said sleeve connected with said crankpin, and a bearing in said sleeve for said crankshaft extension.
 5. The method of punching a muffler core tube comprising supporting said core tube internally for rotation on its axis, and projecting a punch outwardly and circumferentially through said core tube to punch a hole in said tube and bend out a tongue on one side of said hole.
 6. The method of claim 5 including causing said circumferential movement of said punch to rotate said tube into position for punching another hole.
 7. The method of claim 6 including retracting said punch and moving said tube axially after each punching operation to punch a spiral pattern of holes in said tube. 